Though, the NBA calls are more subjective, or up to the opinion of the refs. In NFL, its "where the ball lies" type stuff, but in the nba the fouls are the major calls that are messed up. However, it is difficult to tell how much force is applied and therefore up to the judgment of the refs. Therefore, fans' bias may make them lean one way or another, so instant replay could actually cause more screams of controversy if allowed on fouls (which are the calls that are usually disputed).

In other words, right now you can somewhat forgive a ref for a bad call because you can tell yourself, "Well, he must have missed it." With instant replay, the refs may still feel the call should stand while fans view the call as bogus.